1. Field of the Invention.
The present invention relates to a unitary plastic piston and, more particularly, to a simple, lightweight, long lasting plastic piston.
2. Description of the Prior Art.
In the field of pneumatic and hydraulic cylinders, accumulators, actuators, regulators, valves, and the like, a common mechanical component is a piston which reciprocates within a cylinder. Conventional pistons are made either from steel, cast iron, aluminum, or brass. The pistons reciprocate within cylinders which are also made from metal. Since it is necessary to prevent metal-to-metal contact between the same materials, the pistons and the cylinders are either made from dissimilar metals or wear rings are positioned in grooves in the piston's surface, which rings physically contact the cylinder walls and absorb the load. O-rings and gaskets positioned in other grooves in the piston surface prevent leakage between opposite sides of the piston, but normally do not absorb any of the side load.
Conventional pistons often consist of a large number of interconnected parts. Furthermore, some piston configurations also require multiple wear rings and/or seals made from rubber, plastic, leather, and the like. These separate piston and seal assemblies are expensive due to the need to manufacture each part individually. Since there are multiple components involved, assembly time is also longer and this adds to the expense. The multiple-piece seal and piston assemblies further allow for leakage paths between the individual elements. Furthermore, many seal materials do not provide for a long wear life. Where the piston is manufactured from steel or aluminum, it is quite heavy.
In order to overcome one or more of the above problems, the prior art teaches various experiments using different materials for pistons. It has been known to mold rubber and plastic materials on metal cores. It has also been known to formulate pistons from multiple plastic, rubber, and other material parts and to clamp such parts together. However, none of these attempts have provided an effective piston and seal which is lightweight and inexpensive and has a long life.